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author | Christoph Hellwig <hch@lst.de> | 2009-10-27 11:05:28 +0100 |
---|---|---|
committer | Jan Kara <jack@suse.cz> | 2009-12-10 15:02:50 +0100 |
commit | 6b2f3d1f769be5779b479c37800229d9a4809fc3 (patch) | |
tree | 046ef6736ec6c25ab1c68741ba715d13645af336 /arch/mips/include/asm/fcntl.h | |
parent | 59bc055211b8d266ab6089158058bf8268e02006 (diff) | |
download | kernel_samsung_crespo-6b2f3d1f769be5779b479c37800229d9a4809fc3.zip kernel_samsung_crespo-6b2f3d1f769be5779b479c37800229d9a4809fc3.tar.gz kernel_samsung_crespo-6b2f3d1f769be5779b479c37800229d9a4809fc3.tar.bz2 |
vfs: Implement proper O_SYNC semantics
While Linux provided an O_SYNC flag basically since day 1, it took until
Linux 2.4.0-test12pre2 to actually get it implemented for filesystems,
since that day we had generic_osync_around with only minor changes and the
great "For now, when the user asks for O_SYNC, we'll actually give
O_DSYNC" comment. This patch intends to actually give us real O_SYNC
semantics in addition to the O_DSYNC semantics. After Jan's O_SYNC
patches which are required before this patch it's actually surprisingly
simple, we just need to figure out when to set the datasync flag to
vfs_fsync_range and when not.
This patch renames the existing O_SYNC flag to O_DSYNC while keeping it's
numerical value to keep binary compatibility, and adds a new real O_SYNC
flag. To guarantee backwards compatiblity it is defined as expanding to
both the O_DSYNC and the new additional binary flag (__O_SYNC) to make
sure we are backwards-compatible when compiled against the new headers.
This also means that all places that don't care about the differences can
just check O_DSYNC and get the right behaviour for O_SYNC, too - only
places that actuall care need to check __O_SYNC in addition. Drivers and
network filesystems have been updated in a fail safe way to always do the
full sync magic if O_DSYNC is set. The few places setting O_SYNC for
lower layers are kept that way for now to stay failsafe.
We enforce that O_DSYNC is set when __O_SYNC is set early in the open path
to make sure we always get these sane options.
Note that parisc really screwed up their headers as they already define a
O_DSYNC that has always been a no-op. We try to repair it by using it for
the new O_DSYNC and redefinining O_SYNC to send both the traditional
O_SYNC numerical value _and_ the O_DSYNC one.
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Grant Grundler <grundler@parisc-linux.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger@sun.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Acked-by: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'arch/mips/include/asm/fcntl.h')
-rw-r--r-- | arch/mips/include/asm/fcntl.h | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/mips/include/asm/fcntl.h b/arch/mips/include/asm/fcntl.h index 2a52333..7c6681a 100644 --- a/arch/mips/include/asm/fcntl.h +++ b/arch/mips/include/asm/fcntl.h @@ -10,7 +10,7 @@ #define O_APPEND 0x0008 -#define O_SYNC 0x0010 +#define O_DSYNC 0x0010 /* used to be O_SYNC, see below */ #define O_NONBLOCK 0x0080 #define O_CREAT 0x0100 /* not fcntl */ #define O_TRUNC 0x0200 /* not fcntl */ @@ -18,6 +18,21 @@ #define O_NOCTTY 0x0800 /* not fcntl */ #define FASYNC 0x1000 /* fcntl, for BSD compatibility */ #define O_LARGEFILE 0x2000 /* allow large file opens */ +/* + * Before Linux 2.6.32 only O_DSYNC semantics were implemented, but using + * the O_SYNC flag. We continue to use the existing numerical value + * for O_DSYNC semantics now, but using the correct symbolic name for it. + * This new value is used to request true Posix O_SYNC semantics. It is + * defined in this strange way to make sure applications compiled against + * new headers get at least O_DSYNC semantics on older kernels. + * + * This has the nice side-effect that we can simply test for O_DSYNC + * wherever we do not care if O_DSYNC or O_SYNC is used. + * + * Note: __O_SYNC must never be used directly. + */ +#define __O_SYNC 0x4000 +#define O_SYNC (__O_SYNC|O_DSYNC) #define O_DIRECT 0x8000 /* direct disk access hint */ #define F_GETLK 14 |